[Studies on the refractory coating materials for preventing scale formation (author's transl)]

Area of Science:

• Materials Science
• Metallurgy
• Casting Technology

Context:

• Casting high-fusing alloys like cobalt-chrome and nickel-chrome often results in scale formation due to reactions between the investment mold and molten alloys.
• This scale formation presents a significant disadvantage in achieving smooth and high-quality castings.
• Various coating materials are employed to mitigate this issue.

Purpose:

• To evaluate the effectiveness of seven commercialized coating materials in preventing scale formation during high-fusing alloy casting.
• To analyze the reaction products between coating materials and molten alloys using X-ray diffractometry.
• To determine the impact of different coating compositions on cast surface roughness.

Summary:

• Seven commercial coating materials were tested. Refractory compositions included alpha-quartz (SiO2), zircon (ZrSiO4), and zirconium oxide (ZrO2).
• Coatings primarily containing zircon (Dainainvest) or a combination of alpha-quartz and zircon (Liquid investment, Paint investment) effectively reduced surface roughness with minimal reaction products.
• Coatings composed mainly of alpha-quartz (Quick request, Pre-coat, Ethymay B) were less effective, resulting in rough surfaces due to picrochromite and eskolaite formation. Hi-coat (zirconium oxide) showed minimal improvement.

Impact:

• Identifies specific mold coating compositions, particularly those with zircon, that significantly improve casting quality by reducing surface roughness.
• Provides insights into the material interactions occurring at high temperatures, guiding the selection of optimal coatings for cobalt-chrome and nickel-chrome alloy casting.
• Highlights the limitations of alpha-quartz-based coatings in preventing detrimental reactions and scale formation.